Variable Valve Train With Independent Cam Rotation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing variable valve trains for combustion engines have a rigid and non-variable sequence of switching states, leading to inefficient transitions during abrupt load changes, requiring step-by-step adjustments to reach desired switching states.
Innovation Solution
Two control cams on a common control shaft can rotate independently, allowing seamless switching between 4 cam lift modes without intermediate steps, using a servo mechanism and spring pretensioning for precise control, and enabling independent actuation of valve train elements for improved switchability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a rigid control shaft with fixed cam sequence is used, then the structure is simple and manufacturing is easy, but the switching between cam lift modes cannot be optimized for abrupt load changes
Solution Approach 1:
The control shaft is divided into multiple independently rotatable cam segments (first control cam, second control cam, third control cam) that can rotate relative to each other. This segmentation allows each cam to be controlled independently by separate actuators, enabling flexible and adaptive switching between different cam lift modes without requiring a completely new rigid shaft design.
Solution Approach 2:
The control shaft transitions from a rigid, fixed-sequence structure to a dynamic structure where cam segments can rotate independently. This dynamic capability allows the valve train to adapt to varying load conditions by selectively positioning cam segments to achieve desired lift modes, while the modular design keeps individual components manageable in size and complexity.
2Loss of time
If step-by-step switching is used to reach desired cam lift modes, then the control structure is simple, but time is lost during abrupt load changes
Solution Approach 1:
Multiple control cams are pre-positioned on the control shaft at different angular positions, each representing a different cam lift mode. The independent actuators can directly position any desired cam segment to the active position without requiring sequential step-by-step switching, enabling rapid transition to the required lift mode when load conditions change abruptly.
Solution Approach 2:
Independent actuators serve as intermediaries between the control system and the cam segments. These actuators directly control the rotational position of each cam segment, eliminating the need for mechanical step-by-step switching mechanisms and enabling rapid, automated transitions between different cam lift modes.
3Ease of operation
If multiple actuators are allocated for each cylinder, then precise control of each valve train element is achieved, but the device complexity and cost increase
Solution Approach 1:
The control shaft design allows a limited number of actuators to control multiple cam segments that collectively serve multiple cylinders. Each actuator controls a specific cam segment that can influence multiple valve train elements, enabling one actuator to perform multiple functions and reducing the total number of actuators required while maintaining precise control capability.
Solution Approach 2:
Multiple cam segments are merged onto a single rotating control shaft structure, allowing them to be controlled by fewer actuators. The cam segments work together in a coordinated manner, with their combined action providing precise control over multiple valve train elements across multiple cylinders, reducing the need for separate actuators for each cylinder.
Data Source
AI summary
A variable valve train (1) of a combustion engine for applying a load on two equally acting gas exchange valves (2, 3) for each cylinder of the combustion engine is provided, including a switchable valve train element (4, 5) with an outer part and an inner part ((6, 7), (8, 9)) that can move relative to each other allocated to each of the two gas exchange valves (2, 3). The outer and inner parts ((6, 7), (8, 9)) are selectively connectable to each other by an associated coupling slide mechanism (10, 11). The valve train (1) further includes a control shaft (12), on which a control cam (13, 14) is applied for each coupling slide mechanism (10, 11), and the control cams contact an outer end face (15, 16) of the respective coupling slide mechanisms (10, 11) for displacement thereof in one direction, and the two control cams (13, 14) can rotate separately from each other on the common control shaft (12).